1. Field of the Invention
The present invention relates to improved water-based hydraulic fluid compositions containing selected two-component anti-wear agents.
2. Description of the Prior Art
U.S. Pat. No. 4,434,066, which issued to Lewis on Feb. 28, 1984, discloses a water-based energy transmitting fluid (i.e. water-based hydraulic fluid) which comprises an aqueous composition having a viscosity of at least 10 centistokes at 40.degree. C. and contains (a) up to about 80% by weight water, (b) at least 0.1% by weight of an acidic lubricity agent, and (c) a minimally effective amount of an anti-wear additive (or agent) which comprises (i) a hydroxyl-substituted aromatic carboxylic acid component and (ii) a nitroaromatic compound component.
Although the two-component anti-wear agents disclosed in this Lewis patent do have apparent utility as anti-wear agents, there is still a need in the art for other anti-wear agents which are more effective and more economical to use.
It is an object of the present invention to make effective and economic anti-wear agents from other combinations of aromatic compounds.